The invention relates to a device for spreading liquid binder and roadstone behind a road making machine.
Surface maintenance work of road surfaces by producing on the road surface a coating which is constituted by roadstone and a liquid binder, such as a bitumen emulsion or hot liquid bitumen, is usually carried out according to one of the two techniques which will be described below.
A spreading assembly which is constituted by a bitumen spreader and a roadstone spreader is used in order to produce the coating over large road surfaces. The spreader must spread the binder, which is either an emulsion or hot bitumen, over the highway with very great precision and excellent regularity in the transverse direction of the road surface and the spreading assembly. On the basis of the materials according to the prior art, use is made for this purpose of a rail having multiple jets, that is to say, a rail comprising nozzles which are distributed in the longitudinal direction of the rail which is arranged in the transverse direction of the road surface, with a constant spacing pitch, for example, a pitch of approximately 100 mm. The rail is supplied with liquid binder and the nozzles are constructed so as to produce a conical jet having a cross-section which is elongate in the transverse direction and which is similar to a triangular flat jet which meets the road surface over an impact surface whose length, in the transverse direction, depends on the apex angle of the flat jet and the height of the rail above the road surface. A rail height above the road surface is selected in accordance with the apex angle of the flat jets and the pitch of the nozzles over the rail so that the impact surface of each of the jets has a length of approximately three pitches in the transverse direction. Owing to the overlapping arrangement of the jets which are formed by the successive nozzles, three jets are superimposed on each of the pitches of the impact surface, which provides three coverings of the road surface.
The roadstone is generally deposited on the liquid binder which covers the road surface by a roadstone spreader which comprises a plurality of successive flap-doors of constant width which are distributed in the transverse direction of the road surface and which are controlled in order to open or close them so as to adjust the width for spreading roadstone over the road surface which is covered with liquid binder. In general, the multi-flap roadstone spreader is fixed to the bottom of the bucket of a tipping lorry, in which bucket the roadstone is loaded. In this manner, good transverse distribution is obtained.
This known technique using a spreading assembly results in surface coatings of excellent quality.
The surface maintenance of roads can require the treatment of localised faults, these works being generally designated in the art as emergency patching works. Such works can relate to isolated zones which are more or less circular or strips having a width less than the width of the road surface. In order to carry out such emergency patching works, a manual method has conventionally been used for some time consisting in applying the bitumen with a hand-held nozzle and spreading the roadstone using a roadstone container.
This rudimentary technique is used less and less and it is preferable to use materials which allow emergency patching works to be carried out in an automatic manner. The materials used are machines which combine on the same road making machine a small spreader and a small roadstone bucket which is associated with a roadstone spreader. Such machines have allowed advances in techniques for the surface maintenance of roads by mechanising the repair works and the practical and economic side of such machines which combine two functions explains their current success, in spite of the low level of autonomy thereof on site owing to the relatively small capacity of the roadstone bucket and the reservoir of liquid binder, such machines generally being constituted by a lorry.
A more disruptive disadvantage of this technique is that it leads to surface coatings of poor quality because the technique does not respect the principle which is implemented in spreading assemblies and which consists in depositing the bitumen on the road surface in three coverings. In order to carry out repair work to relatively small surfaces, the bitumen spreading rail is positioned at a height above the road surface which is less than the height usually used on spreading assemblies. Taking into consideration the apex angle of the flat jets and the pitch between the nozzles of the rail, each of the jets forms an impact surface whose dimension in the transverse direction is equivalent to only two pitches and the overlapping of the jets produces only two coverings, by two jets being superimposed over each of the pitches of the impact surface.
In the case of spreading assemblies, the width of the roadstone spreading flap-doors relative to the spacing pitch of the nozzles is further such that three jets of binder are applied over the spreading width of a flap-door. In automatic machines for emergency patching works, only two jets of binder are used per spreading width of a roadstone flap-door. The use of two coverings of binder instead of three and two jets of binder instead of three over a spreading width of a roadstone flap-door leads to surface coatings of lesser quality than that of the coatings obtained by means of a large-width spreading assembly.
Furthermore, local repairs carried out on strips of road surface by known automatic emergency patching techniques include faults along the edges or margins thereof. There are systematically overflows of binder as well as slippage of roadstone at the margins of the repaired strip owing to an under-metering of bitumen at the margins, which is linked structurally to the principle of these automatic machines.
These faults are present even if the binder rails of the automatic emergency patching machines are equipped with nozzles which are identical to the spreaders of the spreading assemblies with the same spacing pitch.
Therefore, the object of the invention is to provide a device for spreading liquid binder and roadstone behind a road making machine comprising at least one binder spreading rail which is fixed to a rear portion of the road making machine, in a transverse direction, and having a first set of nozzles for spreading binder which are distributed over the length of the rail in the transverse direction with a constant spacing pitch and which are directed towards a road surface, on which the road making machine moves, and having adjustable means for supplying the rail with binder in order to supply all or some of the nozzles of the first set in order to form, at the outlet of each of the nozzles, a flat jet having an apex angle such that, in accordance with the height of the rail above the road surface, each jet has an impact surface on the road surface having a width of approximately three pitches in the transverse direction, and such that the jets of the first set of nozzles overlap in such a manner that, for each of the successive pitches of the impact surfaces of the jets, in the transverse direction, three jets are superimposed, and a roadstone spreader which is fixed to the rear of the road making machine, in a transverse arrangement facing the binder spreading rail, for spreading roadstone, comprising a plurality of flap-doors which are of equal width and which are juxtapositioned in the transverse direction and which are associated with control means, in order to open or close them, so as to allow or prevent the passage of a flow of roadstone having a constant width of approximately three pitches at the road surface for each of the flap-doors and to adjust the total spreading width of the roadstone spreader by all or some of the flap-doors being opened, this device allowing coatings of an excellent quality to be produced, at least equivalent to the quality of the coatings produced by spreading assemblies, and in particular emergency patching works to be carried out over strips of relatively small width, with a good level of quality for producing the coating at the margins of the repaired strip.
To this end:
the binder spreading rail further comprises a second set of nozzles which are each interposed between two successive nozzles of the first set of nozzles in the transverse direction and which are constructed so as to produce, when they are supplied with binder by the adjustable supply means of the rail, a first half-jet and a second half-jet each, which jets are successive in the transverse direction and which each have an impact surface of a width substantially equal to one pitch in the transverse direction and which are adjacent at one side and the other of an axis of the nozzle perpendicular to the transverse direction, the first half-jet which is located towards the end of the rail having a flow rate substantially double the flow rate of the second half-jet which is located towards the central portion of the rail, and
the means for supplying the rail with binder are provided in order to ensure a selective supply of nozzles of the second set with a flow rate substantially equal to the supply rate of each of the nozzles of the first set, so that spreading of roadstone and liquid binder is brought about over a road surface width which is equal to a multiple of the spreading width of a flap-door, with two jets of liquid binder being superimposed over one pitch at each of the ends of the road surface width and three jets being superimposed over the other central pitches of the road surface, and with three jets of binder being spread for each of the spreading widths of a flow of roadstone from a flap-door of the roadstone spreader.
The device according to the invention can be constructed in such a manner that:
the flap-doors of the roadstone spreader pour roadstone directly onto the road surface, the spreading width of the roadstone from a flap-door being substantially equal to the width of a flap-door in the transverse direction;
the flap-doors of the roadstone spreader are associated with at least one of a distributor roller, a metering roller or a feeder or counter-feeder, and the spreading width of the roadstone over the road surface is greater than the width of the flap-doors of the roadstone spreader;
the nozzles of the first set and the nozzles of the second set are arranged on the same rail body;
the nozzles of the first set are arranged on a first rail body and the nozzles of the second set are arranged on a second rail body which is parallel with the first rail body;
the nozzles of the second set are each arranged at an identical distance from the nozzles of the first set, between which they are interposed in the transverse direction.
For a better understanding of the invention, a device for spreading liquid binder and roadstone according to the invention and the use thereof for emergency patching works will be described by way of example with reference to the appended Figures.